Effects of frictional properties of quartz and feldspar in the crust on the depth extent of the seismogenic zone

Abstract Earthquake magnitude is closely related to the depth extent of the seismogenic zone, and higher magnitude earthquakes occur where the seismogenic zone is thicker. The frictional properties of the dominant mineral constituents of the crust, such as feldspar-group minerals, control the depth extent of the seismogenic zone. Here, the velocity dependence of the steady-state friction of anorthite, the calcic endmember of the feldspar mineral series, was measured at temperatures from 20 to 600 °C, pore pressures of 0 (“dry”) and 50 MPa (“wet”), and an effective pressure of 150 MPa. The results support previous findings that the frictional properties of feldspar play a dominant role in limiting the depth extent of the seismogenic zone. This evidence suggests that brittle deformation of anorthite may be responsible for brittle fault movements in the brittle–plastic transition zone.

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Frictional Properties of Anorthite (feldspar): Implications for the Lower Boundary of the Seismogenic Zone

10.21203/rs.3.rs-41023/v1 ◽

2020 ◽

Author(s):

Koji Masuda

Keyword(s):

Dominant Role ◽

Lower Boundary ◽

Earthquake Magnitude ◽

Seismogenic Zone ◽

Effective Pressure ◽

Velocity Dependence ◽

Brittle Deformation ◽

Frictional Properties ◽

Depth Extent ◽

Mineral Constituents

Abstract Earthquake magnitude is closely related to the depth extent of the seismogenic zone, and higher magnitude earthquakes occur where the seismogenic zone is thicker. The frictional properties of the dominant mineral constituents of the crust, such as feldspar group minerals, control the depth extent of the seismogenic zone. Here, the velocity dependence of the steady-state friction of anorthite, a member of the feldspar mineral series, was measured at temperatures from 20 to 600 °C, pore pressures of 0 (“dry”) and 50 MPa (“wet”), and an effective pressure of 150 MPa. The results support previous findings that the frictional properties of feldspar play a dominant role in limiting the depth extent of the seismogenic zone. This evidence suggests that brittle deformation of anorthite may be responsible for brittle fault movements in the brittle–plastic transition zone.

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Frictional properties of anorthite (feldspar): Implications for the lower boundary of the seismogenic zone

10.21203/rs.3.rs-41023/v2 ◽

2020 ◽

Author(s):

Koji Masuda

Keyword(s):

Dominant Role ◽

Lower Boundary ◽

Earthquake Magnitude ◽

Seismogenic Zone ◽

Effective Pressure ◽

Velocity Dependence ◽

Brittle Deformation ◽

Frictional Properties ◽

Depth Extent ◽

Mineral Constituents

Abstract Earthquake magnitude is closely related to the depth extent of the seismogenic zone, and higher magnitude earthquakes occur where the seismogenic zone is thicker. The frictional properties of the dominant mineral constituents of the crust, such as feldspar-group minerals, control the depth extent of the seismogenic zone. Here, the velocity dependence of the steady-state friction of anorthite, the calcic endmember of the feldspar mineral series, was measured at temperatures from 20 to 600 °C, pore pressures of 0 (“dry”) and 50 MPa (“wet”), and an effective pressure of 150 MPa. The results support previous findings that the frictional properties of feldspar play a dominant role in limiting the depth extent of the seismogenic zone. This evidence suggests that brittle deformation of anorthite may be responsible for brittle fault movements in the brittle–plastic transition zone.

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Comparison of smectite- and illite-rich gouge frictional properties: application to the updip limit of the seismogenic zone along subduction megathrusts

Earth and Planetary Science Letters ◽

10.1016/s0012-821x(03)00424-2 ◽

2003 ◽

Vol 215 (1-2) ◽

pp. 219-235 ◽

Cited By ~ 351

Author(s):

Demian M Saffer ◽

Chris Marone

Keyword(s):

Seismogenic Zone ◽

Frictional Properties

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Effects of heterogeneity on frictional-viscous deformation and the depth-extent of the seismogenic zone

10.5194/egusphere-egu21-10039 ◽

2021 ◽

Author(s):

Ake Fagereng ◽

Adam Beall

Keyword(s):

Shear Stress ◽

Yield Strength ◽

Fault Zone ◽

Fluid Pressure ◽

Local Stress ◽

Seismogenic Zone ◽

Depth Range ◽

Viscous Deformation ◽

Viscosity Contrast ◽

Depth Extent

Current conceptual fault models define a seismogenic zone, where earthquakes nucleate, characterised by velocity-weakening fault rocks in a dominantly frictional regime. The base of the seismogenic zone is commonly inferred to coincide with a thermally controlled onset of velocity-strengthening slip or distributed viscous deformation. The top of the seismogenic zone may be determined by low-temperature diagenetic processes and the state of consolidation and alteration. Overall, the seismogenic zone is therefore described as bounded by transitions in frictional and rheological properties. These properties are relatively well-determined for monomineralic systems and simple, planar geometries; but, many exceptions, including deep earthquakes, slow slip, and shallow creep, imply processes involving compositional, structural, or environmental heterogeneities. We explore how such heterogeneities may alter the extent of the seismogenic zone.&#160;We consider mixed viscous-frictional deformation and suggest a simple rule of thumb to estimate the role of heterogeneities by a combination of the viscosity contrast within the fault, and the ratio between the bulk shear stress and the yield strength of the strongest fault zone component. In this model, slip behaviour can change dynamically in response to stress and strength variations with depth and time. We quantify the model numerically, and illustrate the idea with a few field-based examples: 1) earthquakes within the viscous regime, deeper than the thermally-controlled seismogenic zone, can be triggered by an increase in the ratio of shear stress to yield strength, either by increased fluid pressure or increased local stress; 2) there is commonly a depth range of transitional behaviour at the base of the seismogenic zone &#8211; the thickness of this zone increases markedly with increased viscosity contrast within the fault zone; and 3) fault zone weakening by phyllosilicate growth and foliation development increases viscosity ratio and decreases bulk shear stress, leading to efficient, stable, fault zone creep. These examples are not new interpretations or observations, but given the substantial complexity of heterogeneous fault zones, we suggest that a simplified, conceptual model based on basic strength and stress parameters is useful in describing and assessing the effect of heterogeneities on fault slip behaviour.&#160; &#160;&#160;&#160;&#160;&#160;&#160;&#160;

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Quantifying effects of laboratory-simulated diagenetic sediment lithification on frictional slip behavior

10.5194/egusphere-egu2020-3396 ◽

2020 ◽

Author(s):

Matt Ikari ◽

Andre Hüpers

Keyword(s):

Plate Boundary ◽

Seismogenic Zone ◽

Low Grade ◽

Depth Range ◽

Experimental Conditions ◽

Frictional Behavior ◽

Frictional Properties ◽

Porosity Reduction ◽

Fault Gouges ◽

Frictional Slip

On major plate-boundary fault zones, it is generally observed that large-magnitude earthquakes tend to nucleate within a discrete depth range in the crust known as the seismogenic zone.&#160; This is generally explained by the contrast between frictionally stable, velocity strengthening sediments at shallow depths and lithified, velocity-weakening rocks at seismogenic (10&#8217;s of km) depth. Thus, it is hypothesized that diagenetic and low-grade metamorphic processes are responsible for the development of velocity-weakening frictional behavior in sediments that make up fault gouges.&#160; Previous laboratory studies comparing the frictional properties of intact rocks and powdered versions of the same rocks generally support this hypothesis, however controlling lithification in the laboratory and systematically quantifying frictional behavior as a function of lithification and remains a challenge.Here, we simulate the lithification process in the laboratory by using mixtures of halite and shale powders with halite-saturated brine, which we consolidate under 10 MPa normal stress and subsequently desiccate.&#160; The desiccation allows precipitation of halite as cement, creating synthetic rocks.&#160; We vary the proportion of salt to shale in our samples, which we use as a proxy for degree of lithification.&#160; We measure the frictional properties of our lithified samples, and equivalent powdered versions of these samples, with velocity-step tests in the range 10-7 &#8211; 3x10-5 m/s.&#160; We quantify lithification by two methods: (1) direct measurement of cohesion, and (2) measuring the porosity reduction of lithified samples compared to powders.&#160; Using these measurements, we systematically investigate the relationship between lithification and frictional slip behavior.We observe that powdered samples of every halite-shale proportion exhibits predominantly velocity-strengthening friction, whereas lithified samples exhibit a combination of velocity strengthening and significant velocity weakening when halite constitutes at least 30 wt% of the sample.&#160; Larger velocity weakening generally coincides with friction coefficients of > 0.62, cohesion of > ~1 MPa, and porosity reduction of > ~50 vol%.&#160; Although none of our lithified samples exhibit strictly velocity-weakening friction, this is consistent with the frictional behavior of pure halite under our experimental conditions.&#160; Scanning electron microscopy images do not show any clear characteristics attributable to velocity-weakening, but did reveal that the shear surfaces for powders tends to exhibit small cracks not seen in the lithified sample shear surfaces.&#160; These results suggest that lithification via cementation and porosity loss may facilitate slip instability, but that microstructural indicators are subtle.

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Strike-variable coseismic and postseismic slips of the 12 December 2017 Mw 6.0 Hojedk (Iran) earthquake revealed by Sentinel-1/2 images: Implications for the local lithospheric structure

10.5194/egusphere-egu2020-12085 ◽

2020 ◽

Author(s):

Yingwen Zhao ◽

Caijun Xu ◽

Yangmao Wen

Keyword(s):

Slip Distribution ◽

Seismogenic Zone ◽

Postseismic Deformation ◽

Reverse Fault ◽

Sar Images ◽

One Year ◽

The Moment ◽

Depth Extent ◽

Postseismic Slip ◽

Sentinel 2

On 12 December 2017, a shallow reverse earthquake ruptured an unrecognized fault located in a transpressional relay zone between Lakar Kuh and Gowk faults. Four tracks of Sentinel-1A/B interferometric wide swath SAR images are used to generate coseismic interferograms. The retrieved maximum line-of-sight (LOS) displacement is up to ~1 m toward the satellite for descending data. An offset tracking method within GAMMA software is used to generate range and azimuth offsets based on Sentinel-1 SAR images. Two Sentinel-2 images are processed with the COSI-Corr package to generate horizontal displacements. The calculated three-dimension deformation field shows that the east-west displacements have motions in different directions, the north-south shortening near the fault trace approaches ~2 m and the maximum uplift is over 1 m. Based on the rupture trace in Sentinel-2 image, a strike-variable fault is constructed to explain the LOS displacements. The estimated slip distribution shows that the peak slip is ~2.5 m located at a depth of ~1.5 km and the depth extent of rupture is 0-3 km with the length of rupture on the surface approaching ~7 km. There are both right-lateral and left-lateral slips occurring on the fault, which are consistent with field observations. The one year of postseismic displacements are estimated by a short baseline subset technique based on two tracks (ascending and descending) of Sentinel-1 SAR images. The maximum LOS displacements is up to ~7 cm toward the satellite for the descending data. The forward displacements show that the poro-elastic rebound in the upper crust does not explain the LOS data. The data can be fitted well in terms of afterslip. The estimated postseismic slip on this strike-variable fault is found to occur in portions of the fault where small slips on these patches are obtained in the coseismic slip inversion. Most of patches related to the postseismic slip are located below the main coseismic patches with the depth extent of rupture being 0.5-4 km. The cumulative slip distribution during one year has the peak slip of ~20 cm, releasing ~12% of the moment of coseismic rupture. Taking into account aftershock depths, the shallow postseismic slip is considered to occur aseismically and cause the most of postseismic deformation. The afterslip may result from some response to a stress concentration located at the periphery of main coseismic rupture. After the analysis on Coulomb stress change, it is possible that the former two Mw ~6 earthquakes occurred on 1 and 12 December cause stress perturbations in the seismogenic zone of this earthquake, which further may bring the local prestressed lithosphere to rupture. For this shallow event, a small shear modulus (less than 30 GPa) is needed to make the moment more comparable to seismic results. This earthquake can be interpreted as the accommodation of the northward motion in the form of oblique-slip reverse fault between right-lateral strike-slip fault systems. The unusually deformation patterns caused by the coseismic and postseismic slips of this earthquake may be indicative of differently local lithosphere structure in this transpressional relay zone.

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Influence of crustal lithology and the thermal state on microseismicity in the Wakayama region, southern Honshu, Japan

Earth Planets and Space ◽

10.1186/s40623-021-01503-3 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Sumire Maeda ◽

Shinji Toda ◽

Toru Matsuzawa ◽

Makoto Otsubo ◽

Takumi Matsumoto

Keyword(s):

Thermal State ◽

Upper Crust ◽

Intraplate Earthquakes ◽

Regional Seismicity ◽

Frictional Properties ◽

Rock Types ◽

Temperature Ranges ◽

Depth Extent ◽

Hypocenter Depth ◽

Pelitic Rocks

AbstractHere we investigate the influence of the lithology and thermal state of the upper crust on earthquake distributions beneath the Wakayama region, southern Honshu, Japan, to better understand the influence of crustal conditions on regional seismogenesis. The earthquakes are concentrated in the deeper sections of mafic belts and shallower sections of pelitic belts, based on a comparison of relocated hypocenters and estimated subsurface geological structures. We compare the frictional properties of pelitic rocks and basalt, as obtained from petrological experiments, with the hypocenter depth distributions in pelitic and mafic belts to assess the control of crustal lithology on the depth extent of regional seismicity. The earthquake distributions are consistent with the temperature ranges over which the respective rock types are expected to exhibit a velocity-weakening behavior, based on the petrological experiments. The results suggest that the occurrence of shallow intraplate earthquakes is controlled by the temperature- and lithology-dependent friction of the upper crust.

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Large-displacement, hydrothermal frictional properties of DFDP-1 fault rocks, Alpine Fault, New Zealand: Implications for deep rupture propagation

10.26686/wgtn.13819181.v1 ◽

2021 ◽

Author(s):

AR Niemeijer ◽

Carolyn Boulton ◽

VG Toy ◽

John Townend ◽

Rupert Sutherland

Keyword(s):

New Zealand ◽

Phase 1 ◽

Rupture Propagation ◽

Low Velocity ◽

Fault Rocks ◽

Frictional Properties ◽

Alpine Fault ◽

Rate And State Friction ◽

Fault Gouges ◽

Depth Extent

©2016. The Authors. The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65-75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction. Friction remains more or less constant with changes in temperature, but a transition from velocity-strengthening behavior to velocity-weakening behavior occurs at a temperature of T = 150°C. The transition depends on the absolute value of sliding velocity as well as temperature, with the velocity-weakening region restricted to higher velocity for higher temperatures. Friction was substantially lower for low-velocity shearing (V < 0.3 μm/s) at 600°C, but no transition to normal stress independence was observed. In the framework of rate-and-state friction, earthquake nucleation is most likely at an intermediate temperature of T = 300°C. The velocity-strengthening nature of the Alpine Fault rocks at higher temperatures may pose a barrier for rupture propagation to deeper levels, limiting the possible depth extent of large earthquakes. Our results highlight the importance of strain rate in controlling frictional behavior under conditions spanning the classical brittle-plastic transition for quartzofeldspathic compositions.

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